1. Field of the Invention
The present invention relates to a stage apparatus and an exposure apparatus; for example, it relates to a stage apparatus and an exposure apparatus that are optimal for use when performing so-called liquid immersion exposure, in which a liquid is supplied onto a substrate to perform exposure.
2. Description of Related Art
Semiconductor devices and liquid crystal display devices are manufactured by a so-called photolithography technique that transfers a pattern formed on a mask onto a photosensitive substrate.
The exposure apparatus used in this photolithography process has a mask stage that supports a mask and a substrate stage that supports a substrate, and it transfers the pattern of the mask to the substrate via a projection optical system while sequentially moving the mask stage and the substrate stage. In recent years, higher resolutions for projection optical systems have been in demand to handle the even higher integration of device patterns. The resolution of the projection optical system is higher the shorter the exposure wavelength used and the larger the numerical aperture of the projection optical system. For this reason, the exposure wavelength used in exposure apparatuses has become shorter year by year, and the numerical aperture of the projection optical system is also increasing. In addition, the mainstream exposure wavelength at present is the 248 nm of a KrF excimer laser, but a shorter wavelength, the 193 mm of an ArF excimer laser, is also coming into practical application. In addition, when exposure is performed, the depth of focus (DOF) is also important in the same way as the resolution. The resolution R and the depth of focus δ are expressed by the respective equations below.R=k1·λ/NA  (1)δ=±k2·λ/NA2  (2)
Here, λ is the exposure wavelength, NA is the numerical aperture of the projection optical system, and k1 and k2 are process coefficients. Based on Equation (1) and Equation (2), it is apparent that when the exposure wavelength λ is made shorter to increase the numerical aperture NA in order to increase the resolution R, the depth of focus δ becomes narrower.
At such times, when the depth of focus δ is too narrow, it is difficult to match the substrate surface to the image plane of the projection optical system, and there is concern that the margin during the exposure operation will be insufficient.
Therefore, the liquid immersion method disclosed in PCT International Patent Publication No. WO 99/49504, for example, has been proposed as a method of essentially shortening the exposure wavelength and broadening the depth of focus. In this liquid immersion method, the space between the lower surface of the projection optical system and the substrate surface is filled with a liquid such as water or an organic solvent to form a liquid immersion region, and the fact that the wavelength of the exposure light in liquid becomes 1/n in air (n is normally approximately 1.2 to 1.6 at the refractive index of the liquid) is used to increase the resolution while expanding the depth of focus to approximately n times.
In the conventional apparatus, when exchanging a substrate for which exposure processing has ended, it is necessary to move the substrate stage to the substrate exchange position (loading position). At this time, the substrate stage moves away from a position that opposes the projection optical system, so it is necessary to stop supply of the liquid while recovering the supplied liquid to avoid the liquid leaking out while recovering the supplied liquid. In addition, after substrate exchange, it is necessary to fill liquid between the projection optical system and the substrate stage, so there are problems in that there is a great loss of time, and throughput drops.
In addition, drying is performed through recovery of the liquid, so there is a problem in that water marks are produced on the projection optical system, and there is a problem in that temperature changes occur in the projection lens, the liquid supply nozzle, etc. due to heat of vaporization.
Therefore, it is thought that even when the substrate stage has been moved to the loading position, the substrate stage (or a liquid immersion region forming member provided on the substrate stage) is made larger so that a liquid immersion region continues to be formed in the space with respect to the projection optical system, but in this case, a problem occurs in that this leads to an increase in the weight of the substrate stage, and throughput drops. In addition, since it becomes necessary to increase the distance between an interferometer, which is provided to obtain substrate position information, and the movable mirror, this leads to the problems of a larger apparatus and a reduction in measurement accuracy.
These problems are not limited to when the substrate stage moves to the loading position, and, as shown in Japanese Unexamined Patent Application Publication No. H10-214783, it occurs in the same way during stage exchange in a twin stage type stage apparatus in which substrate stages are plurally exchangeably provided.
A purpose of some aspects of the invention is to provide a stage apparatus and an exposure apparatus that make possible stage movement without causing throughput to decrease.